Interestingly, while HDACs (histone deacetylases) contribute to deacetylation process of histone marks regardless of acetylated residues, HDAC2 (histone deacetylase 2) levels were increased in AD samples [59], and the administration of various pan-HDAC inhibitors (HDACis) was able to restore associative memory in APP/PS1D9 mice, a model for AD-like pathology [60,61]. This evidence concerns the gene HDAC2 and Alzheimer disease.